In order to understand the effects of ethanol on humans we must first identify the molecular targets for ethanol toxicity. These molecules will be prime candidates for the diagnosis of genetic predisposition to alcoholism and for investigations into therapy for alcohol-related disorders. The broad objective of this proposal is to identify molecular targets for ethanol toxicity by means of genetic screens in the model organism Dictyostelium discoideum. cAMP signal transduction is one of the likely targets for ethanol toxicity in mammals, and the molecular mechanisms that mediate cAMP signaling are highly conserved between evolutionary divergent organisms. In Dictyostelium, as in humans, cAMP signaling is sensitive to the effects of ethanol. However, genetic studies in Dictyostelium are far less complicated then in other organisms, partly because the cAMP signal transduction mechanism is dispensable for growth. This provides a powerful genetic model in which cAMP signaling genes can be manipulated by deletion, over expression, and other mutations. Consequences of the genetic manipulations can be monitored as changes in multicellular development and in spore germination, processes that are highly dependent on cAMP signal transduction. The experimental goals of this proposal are to determine whether known genes in Dictyostelium cAMP signaling are relevant targets for ethanol toxicity, and to select for new mutants with altered ethanol sensitivity. Following identification and characterization of the relevant genes, human homologs will be cloned and expressed in mutants Dictyostelium cells. Humans genes that complement ethanol related mutations in Dictyostelium are likely to be molecular targets for ethanol toxicity. Dictyostelium strains that express the human genes may provide a convenient experimental model that will facilitate future studies in humans.